KR100209425B1 - Method for making overhang construction in lift off process - Google Patents

Abstract

The present invention relates to a lift-off process for forming a metal wiring of a thin-film type optical path adjusting device used in a projection type image display apparatus, and forms an overhang structure without using a separate solution such as monochromobenzene (MCB) A step of cleaning and drying a surface of a wafer on which a base layer, which is one of a plurality of layers constituting an actuator of the thin-film type optical path adjusting apparatus, is formed; and a step of cleaning the surface of the wafer on which a layer of the actuator is formed, A step of applying a resist (PR) to form a photosensitive layer; a step of soft-baking the wafer on which the photosensitive layer is formed to remove a solvent in the photoresist (PR) A step of aligning and exposing the double-sided photoresist (PR) to an inverter baking Forming the overhang structure by a method comprising a step of inverting the characteristics of the photoresist (PR) layer by front exposure and a step of removing a part of the photoresist (PR) layer by development, thereby simplifying the manufacturing process and reducing the cost .

Description

How to build overhang structure

The present invention relates to a thin film optical path adjusting apparatus used in a projection display apparatus, and more particularly, to a method of forming an overhang structure in a lift-off process used for forming a pattern of a metal layer among a plurality of layers of an actuator.

In general, an image display apparatus is classified into a direct view type image display apparatus and a projection image display apparatus according to a display method.

The direct-view type image display device has a CRT (Cathode Ray Tube: hereinafter, referred to as 'CRT') or the like. Such a CRT image display device has a good image quality but increases in weight and thickness as the screen becomes larger, There is a limitation in providing a large screen.

The projection-type image display apparatus includes a large-screen liquid crystal display (hereinafter referred to as LCD), and the weight of the large-screen LCD can be reduced.

However, since the loss of light due to the polarizing plate is large in such an LCD, and the thin film transistor for driving the LCD is formed for each pixel, the light efficiency is very low since it has a limit to increase the aperture ratio (light transmission area).

Accordingly, a projection type image display device using an Actuated Mirror Arrays (hereinafter, referred to as 'AMA') has been developed.

A projection type image display apparatus using AMA separates white light emitted from a light source into red, green, and blue light, and then changes the optical path by driving the optical path adjusting device including the actuators.

That is, the actuator is mounted on the actuators, and the actuators are individually driven to reflect mirrors, which are tilted, respectively, thereby changing the light path, thereby adjusting the amount of light and projecting the light onto the screen. Therefore, an image appears on the screen.

In the above, the actuator tilts the mirror by using an electric field generated and deformed by a voltage applied to the deformed portion made of piezoelectric or electrostrictive ceramics.

The AMA is classified into a one-dimensional AMA and a two-dimensional AMA according to the driving method. In one-dimensional AMA, mirrors are arranged in an M × 1 array, and in a two-dimensional AMA, mirrors are arranged in an M × N array. Accordingly, the projection type image display apparatus using the one-dimensional AMA linearizes M × 1 light beams using the scanning mirror, and the projection type image display apparatus using the two-dimensional AMA projects an image by projecting M × N light beams.

In addition, the actuator is classified into a bulky type and a thin film type according to the shape of the deformed portion. In the bulk type, a ceramic wafer, on which a metal electrode is formed by cutting a thin layer of a multilayer ceramic, is mounted on a driving substrate and then processed by sawing or the like, and a mirror is mounted. However, since the bulk actuator needs to separate the actuators by sawing, a long process time is required and the response speed of the deformed part is slow. Therefore, a thin film type actuator that can be manufactured using a semiconductor process has been developed.

On the other hand, a lift-off process is used to form the wiring of the metal layer such as a plug metal for electrical connection between the lower electrode and the active element, which function as signal electrodes among the plurality of layers constituting the actuator.

The lift-off process is a process used to form a pattern such as a metal wiring, and includes three steps in which the pattern size of the wafer can be changed during a photomasking process such as exposure, development, etching, Since the lift-off process is not used, it is possible to prevent the pattern size of the wafer due to the etching from being changed, and also, It has been used in the wiring process of a metal layer such as a plug metal because it can prevent attack by etching.

In order to facilitate the lift-off process in the lift-off process, the surface of the PR layer is coated with monochlorobenzene (MCB) And the surface of the cured PR is developed to be slower than the surface of the cured PR when the photosensitive layer 130 is developed. Thus, the photosensitive layer 130 has an overhang structure.

An object of the present invention is to provide a method of forming an overhang structure without using a separate solution such as monochlorobenzene (MCB) by using a double-sided PR.

Therefore, in order to achieve the above object, in the present invention, in the lift-off step of forming the pattern of the metal wiring of the thin-film type optical path adjusting device used in the projection type image display apparatus, in any one of a plurality of layers constituting the actuator of the thin- A step of cleaning and drying a surface of a wafer on which a base layer having one layer is formed; a step of forming a photosensitive layer by applying a bi-directional photoresist (PR) on a surface of a layer on which any one of a plurality of layers constituting the actuator is formed; Removing the solvent in the photoresist (PR) by soft baking the wafer on which the photosensitive layer is formed; aligning the mask with the wafer to expose the wafer; Inverting its characteristics by inverter baking and front exposure; And a step of removing a part of the photoresist (PR) layer by development.

FIG. 1 is a cross-sectional view schematically showing a unit pixel of a general M × N thin film type optical path adjusting device. FIG.

2a through 2e are sectional views sequentially showing a method of forming an overhang structure according to the present invention.

DESCRIPTION OF THE REFERENCE NUMERALS

100: wafer 310: target layer

320: photosensitive layer 325: pattern part

330: Mask

Hereinafter, preferred embodiments of the present invention will be described in detail with reference to the accompanying drawings.

2A to 2E are process views sequentially illustrating a method of forming an overhang structure according to the present invention. The constituent members are a wafer 100, a base layer 310, a photosensitive layer 320, and a mask 330, The same reference numerals are used in the first and the same members schematically showing the lift-off process.

First, as shown in FIG. 2A, the surface of the PR is washed with high pressure so that it can adhere well to the surface of the wafer 100 on which the base layer 310, which is one of a plurality of layers constituting the actuator, is formed, 2000 to 40001 bs / in ² , and since only clean water contacts the wafer 100, there is no secondary contamination, and an anti-static agent for preventing static charge is mixed with water.

On the other hand, after the wafer 100 is cleaned, the moisture of the surface of the wafer 100 is removed so that the PR adheres well to the surface of the wafer 100, and the surface characteristics of the wafer 100 are made hydrophobic Conduction, Convection, Radiation, Baking and the like are used for the dehydration process in this case.

Thereafter, the photoresist layer 320 is formed on the surface of the clean and dry wafer 100 by spin coating to a predetermined thickness by a spin coating process to form a photosensitive layer 320 as shown in FIG. 2b, At this time, the thickness of PR is determined by the viscosity and spin rate of PR.

Meanwhile, in one embodiment according to the present invention, the PR uses AZ 5214E as the double-sided PR, and the double-sided PR has both positive and negative sides and is usually a positive type And is changed to a negative type by heat treatment and light treatment.

Thereafter, a convection oven, a moving belt IR oven, a microwave oven, a microwave oven, and a microwave oven are used to facilitate alignment of the mask 330 and improve the adhesion between the wafer 100 and the PR. The soft baking treatment is performed in the same manner as the Conduction Belt Oven to remove the solvent in the PR.

On the other hand, if the solvent in the PR remains, the chemical reaction due to the exposure of the polymer is disturbed and the PR does not adhere well to the surface.

Thereafter, a dark field mask 330 is arranged in an upper portion of the photosensitive layer 320 by manual or automatic alignment, and a contact, a proximity, a projection, UV, Ultra Violet (DUV), or X-RAY is exposed through the dark field mask 330 to the photosensitive layer 320 (see FIG. 2C) ).

The reason why the dark field mask 330 is used is that the double-sided PR acts as a positive PR because the photosensitive layer 320 is a double-sided PR but has no characteristic deformation due to heat treatment and exposure .

On the other hand, by the exposure, the pattern of the dark field mask 330 is transferred to the photosensitive layer 320, and the pattern portion 325 exposed through the transparent mask pattern of the dark field mask 330 is non-multiplexed, The non-visible portion that is not exposed to light by the opaque portion of the field mask remains in a multiplexed state. At this time, the non-multiplexed part has an overhang structure according to the present invention by a subsequent process.

Thereafter, in order to change the characteristics of the double-sided PR constituting the photosensitive layer 320 from positive PR to negative PR, for 60 to 80 seconds (more preferably 70 seconds) at 100 to 140 占 폚 (more preferably 120 占 폚) After the inverter baking, as shown in FIG. 2d, the h-line is exposed to the entire surface of the photosensitive layer 320 at an energy range of 900 to 1100 mJ / cm ² .

On the other hand, the photosensitive layer 320 changes its characteristics from positive PR to negative PR due to the inverter baking and the front exposure, so that the multiplexed portion of the photosensitive layer 320 is not multiplexed, and the non- do.

Then, the photosensitive layer 320 is developed by an immersion method or a spray development process in order to remove non-multiplexed portions except the multiplexed portion of the photosensitive layer 320.

Thus, the overhang structure is formed by the method according to the present invention as shown in FIG.

In particular, in one embodiment of the present invention, development is carried out using an injection method, followed by washing with a washing solution to stop the developing process. At this time, xylene is used as a developing solution and N-butyl acetate is used as a washing solution .

While the present invention has been particularly shown and described with reference to exemplary embodiments thereof, it is to be understood that the invention is not limited to the disclosed exemplary embodiments. .

By the above-described process according to the present invention, an overhang structure is formed without a separate solution such as monochlorobenzene, thereby simplifying the process and reducing the cost.

Claims (5)

In a lift-off step of forming a pattern of a metal wiring of a thin-film type optical path adjusting device used in a projection type image display apparatus, a wafer having a base layer formed of any one of a plurality of layers constituting a plurality of layers of an actuator of the thin- Washing and drying the surface of the substrate; Forming a photosensitive layer by applying a double-sided photoresist on the wafer; Soft-baking the wafer to remove the solvent in the photoresist; Aligning a mask on the wafer and exposing the wafer; Reversing the characteristics of the double-side photoresist by inverter baking and front exposure; And removing a part of the photoresist layer by development. The method of forming an overhang structure according to claim 1, wherein the inverter baking is performed in a temperature range of 100 to 140 占 폚. The method of forming an overhang structure according to claim 1 or 2, wherein the baking of the inverter is performed for 60 to 80 seconds. The method of forming an overhang structure according to claim 1, wherein the front exposure uses h-ling as a light source. The method of forming an overhang structure according to claim 1 or 4, wherein the front exposure is performed at an energy of 900-1100 mJ / cm ² .